We present the results of a VLT MUSE/FORS2 and Spitzer survey of a unique compact lensing cluster CLIO at z = 0.42 , discovered through the GAMA survey using spectroscopic redshifts .
Compact and massive clusters such as this are understudied , but provide a unique prospective on dark matter distributions and for finding background lensed high-z galaxies .
The CLIO cluster was identified for follow up observations due to its almost unique combination of high mass and dark matter halo concentration , as well as having observed lensing arcs from ground based images .
Using dual band optical and infra-red imaging from FORS2 and Spitzer , in combination with MUSE optical spectroscopy we identify 89 cluster members and find background sources out to z = 6.49 .
We describe the physical state of this cluster , finding a strong correlation between environment and galaxy spectral type .
Under the assumption of a NFW profile , we measure the total mass of CLIO to be M _ { 200 } = ( 4.49 \pm 0.25 ) \times 10 ^ { 14 } M _ { \odot } .
We build and present an initial strong-lensing model for this cluster , and measure a relatively low intracluster light ( ICL ) fraction of 7.21 \pm 1.53 % through galaxy profile fitting .
Due to its strong potential for lensing background galaxies and its low ICL , the CLIO cluster will be a target for our 110 hour JWST ‘ Webb Medium-Deep Field ’ ( WMDF ) GTO program .